Tuesday, June 09, 2020

A new mechanism improves the efficiency of antibacterial surfaces

by Universitat Rovira i Virgili

Resistance to antibiotics has become a serious public health problem. Hospital infections, prostheses or surgical implants that become infected and do not respond to treatment are a real challenge to the research community, which has been seeking alternatives for effectively eliminating these bacteria for years. In 2012 the researchers from the Department of Chemical Engineering of the Universitat Rovira i Virgili, Vladimir Baulin and Sergey Pogodin, opened a line of research to develop antibacterial models that were inspired by insects. The wings of, for example, dragon flies are made up of complex structures of nanometric geometric shapes, which are highly efficient at killing bacteria. In their attempt to understand these forms and reproduce them as new anti-bacterial materials, a team consisting of Vladimir Baulin, Marc Werner, from the Leibniz-Institut für Polymerforschung (Dresden, Germany) and Elena Ivanova from the Australian university RMIT, discovered that the elasticity of nanopillars is a key factor because they can retain and release sufficient energy to kill the bacteria.

The line of research that had been initiated years before had already found that the wings of these insects are made up of a structure of nanopillars that eliminates bacteria mechanically, which is known as the biocide effect. These mechano-bactericidal properties—by which bacteria are killed almost instantly when they come into contact with the pillars without any need to use a chemical substance—raises numerous questions that researchers are attempting to answer by experimenting with different shapes and geometries that will help them to understand which has the most efficient bactericidal effect.

They investigated the bactericidal capacity on nanometric surfaces by varying the height of the pillars and keeping the other dimensions constant. The results, which have just been published in the journal PNAS, have shown that the flexibility of these pillars is closely connected to their appearance. "Even the solid and rigid materials become flexible if one of the dimensions is much longer than the others (for example, a guitar string or a long pillar)," says Vladimir Baulin. The researchers have developed a physical model that shows that when bacteria come into contact with these pillars they can accumulate elastic energy even at such a small scale. Thanks to this model it is now possible to calculate the elastic response of other structures and optimize their antibacterial properties.

The deformation forces of the pillar caused by the contact of the bacteria are so high that they can even break the bacteria's cell wall, thus providing a new mechanism for killing them. These forces are associated with surface tensions imposed on the bacterial cells. The pillars under the bacteria that approach stretch more at the edges, whereas the pillars located under the center of the bacteria practically do not change. The study shows, then, that the gradual variation in the height of the pillars of a nanometric surface can determine their bactericidal efficacy.

This discovery may lead to a completely new class of antibacterial materials, which could range from packaging for food to filters or masks. Unlike traditional filters, where the bacteria remain but are not deactivated, the new nanoscale elastic material can safely kill the bacteria in a matter of minutes, which means that they cannot activate any defense mechanisms or give any resistance at all," concluded Baulin

Insect wings hold antimicrobial clues for improved medical implants

More information: Elena P. Ivanova et al, The multi-faceted mechano-bactericidal mechanism of nanostructured surfaces, Proceedings of the National Academy of Sciences (2020). DOI: 10.1073/pnas.1916680117

Journal information: Proceedings of the National Academy of Sciences

Provided by Universitat Rovira i Virgili

Unexpected uncertainty can breed paranoia, researchers find

by Yale University

Pixabay/CC0 Public Domain

In times of unexpected uncertainty, such as the sudden appearance of a global pandemic, people may be more prone to paranoia, Yale University researchers suggest in a new study published in the journal eLife.

"When our world changes unexpectedly, we want to blame that volatility on somebody, to make sense of it, and perhaps neutralize it,'' said Yale's Philip Corlett, associate professor of psychiatry and senior author of the study. "Historically in times of upheaval, such as the great fire of ancient Rome in 64 C.E. or the 9/11 terrorist attacks, paranoia and conspiratorial thinking increased."

Paranoia is a key symptom of serious mental illness, marked by the belief that other people have malicious intentions. But it also manifests in varying degrees in the general population. For instance, one previous survey found that 20% of the population believed people were against them at some time during the past year; 8% believed that others were actively out to harm them.

The prevailing theory is that paranoia stems from an inability to accurately assess social threats. But Corlett and lead author Erin Reed of Yale hypothesized that paranoia is instead rooted in a more basic learning mechanism that is triggered by uncertainty, even in the absence of social threat.

"We think of the brain as a prediction machine; unexpected change, whether social or not, may constitute a type of threat—it limits the brain's ability to make predictions," Reed said. "Paranoia may be a response to uncertainty in general, and social interactions can be particularly complex and difficult to predict."

In a series of experiments, they asked subjects with different degrees of paranoia to play a card game in which the best choices for success were changed secretly. People with little or no paranoia were slow to assume that the best choice had changed. However, those with paranoia expected even more volatility in the game. They changed their choices capriciously—even after a win. The researchers then increased the levels of uncertainty by changing the chances of winning halfway through the game without telling the participants. This sudden change made even the low-paranoia participants behave like those with paranoia, learning less from the consequences of their choices.

In a related experiment, Yale collaborators Jane Taylor and Stephanie Groman trained rats, a relatively asocial species, to complete a similar task where best choices of success changed. Rats who were administered methamphetamine—known to induce paranoia in humans—behaved just like paranoid humans. They, too, anticipated high volatility and relied more on their expectations than learning from the task.

Reed, Corlett and their team then used a mathematical model to compare choices made by rats and humans while performing these similar tasks. The results from the rats that received methamphetamine resembled those of humans with paranoia, researchers found.

"Our hope is that this work will facilitate a mechanistic explanation of paranoia, a first step in the development of new treatments that target those underlying mechanisms," Corlett said.

"The benefit of seeing paranoia through a non-social lens is that we can study these mechanisms in simpler systems, without needing to recapitulate the richness of human social interaction," Reed said.

Explore further

London cyclists feel paranoid road users are out to get them
More information: Erin J Reed et al, Paranoia as a deficit in non-social belief updating, eLife (2020). DOI: 10.7554/eLife.56345
Journal information: eLife

Close-up view reveals binary proto-stars in the process of assemblage
JUNE 9, 2020

by Max Planck Society

]

Zoom into the Ophiuchus molecular cloud, highlighting the star forming system IRAS 16293-2422 with the proto-star B in the upper right corner and the now clearly identified binary proto-stars A1 and A2 on the bottom left. The binary system is shown also in a further zoom-in panel. Credit: MPE; background: ESO/Digitized Sky Survey 2; Davide De Martin

High-resolution observations of a young star forming system clearly unveil a pair of proto-stars at their earliest stages of evolution deeply embedded within the source IRAS 16293-2422 in the Ophiuchus molecular cloud. The team led by the Max Planck Institute for Extraterrestrial Physics used the ALMA interferometer not only to pin down the source configuration, but also to measure the gas and stellar kinematics, determining the mass of the young binary. The two close proto-stars are somewhat heavier than previously thought and they revolve around each other once in about 400 years.

The system called IRAS 16293-2422 is one of the brightest star-forming regions in our neighborhood. It is located in the Ophiuchus molecular cloud at a distance of about 460 light-years and has been widely studied, also because it shows strong emission of numerous complex organic molecules, building blocks of pre-biotic species. However, until now the detailed configuration of the region was unclear, with observations at different wavelengths showing multiple compact sources at slightly different locations. This confusion was due to the large amount of material in front of the nascent proto-stars, expected at these earliest stages of formation.

An international team of astronomers led by the Max Planck Institute for Extraterrestrial Physics (MPE) has now obtained high-resolution radio observations with the ALMA interferometer, which clearly reveals two compact sources A1 and A2 in addition to the well-known proto-star B (see Fig. 1). "Our observations confirm the location of the two close proto-stars and reveal that each is surrounded by a very small dust disk. Both, in turn, are in turn embedded in a large amount of material showing complex patterns" remarks María José Maureira from MPE, the lead author of the study.

Detailed view of the binary proto-star system with a size comparison to our solar system. The separation between the sources A1 and A2 is roughly the diameter of the Pluto orbit. The size of the disk around A1 (unresolved) is about the diameter of the asteroid belt. The size of the disk around A2 is about the diameter of the Saturn orbit. Credit: MPE

The source A1 has a mass of a bit less than 1 solar mass and is embedded in a small dust disk about the size of the asteroid belt; the source A2 has a mass of about 1.4 solar masses and is embedded in a somewhat larger disk (see Fig. 2). Interestingly, this disk around A2 also appears at an angle compared to the overall orientation of the larger cloud structure, while the disk around the source B—at a much larger distance—is seen face-on, indicating a rather chaotic formation history.

In addition to direct imaging of the dust emission, the team also obtained information on the motion of the gas around the stars through observations of spectral lines of organic molecules, which well trace the high-density region surrounding the discovered binary system. This allowed them to get an independent mass measurement and to confirm that A1 and A2 form a bound pair.

Relative motion of A1 (blue) with respect to A2 (red) overlaid on the ALMA continuum observation. The visual impression that A1 orbits around A2 is confirmed through a detailed analysis of the motion of the proto-stars over a 30-year period. Credit: MPE

Combining their latest observations with data collected over the past 30 years, the team found that the two stars orbit each other once every 360 years at a distance similar to the extent of Pluto's orbit, where the orbit is tilted by about 60° (see Fig. 3). "This is the first time that we were able to derive the full orbital parameters of a binary system at this early stage of star formation," points out Jaime Pineda from MPE, who contributed to the modelling.

"With these results we are finally able to dive into one of the most embedded and youngest proto-stellar systems, unveiling its dynamical structure and complex morphology, where we clearly see filamentary material connecting the circumstellar disks to the surrounding region and likely to the cirbumbinary disk. The small disks are probably still being fed and growing!" emphasizes Paola Caselli, director at MPE and head of the Center for Astrochemical Studies. "This was only possible thanks to the great sensitivity of ALMA and the observations of molecules which uniquely trace these dense regions. Molecules send us signals at very specific frequencies, and, following changes of such frequencies across the region (due to internal motions) one can reconstruct the complex kinematics of the system. This is the power of astrochemistry."

Explore furtherAstronomers observe how two suns collect matter in a binary system
More information: Orbital and mass constraints of the young binary system IRAS 16293-2422 A: arXiv:2005.11954 [astro-ph.SR] arxiv.org/abs/2005.11954
Provided by Max Planck Society
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Study reveals birth defects caused by flame retardant

by University of Georgia

Credit: Pixabay/CC0 Public Domain

A new study from the University of Georgia has shown that exposure to a now-banned flame retardant can alter the genetic code in sperm, leading to major health defects in children of exposed parents.

Published recently in Scientific Reports, the study is the first to investigate how polybrominated biphenyl-153 (PBB153), the primary chemical component of the flame retardant FireMaster, impacts paternal reproduction.

In 1973, an estimated 6.5 million Michigan residents were exposed to PBB153 when FireMaster was accidentally sent to state grain mills where it made its way into the food supply. In the decades since, a range of health problems including skin discoloration, headache, dizziness, joint pain and even some cancers have been linked to the exposure.

More striking, the children of those who were exposed seemed to experience a host of health issues as well, including reports of hernia or buildup in the scrotum for newborn sons and a higher chance of stillbirth or miscarriage among adult daughters.

Yet, little work has been done to understand how the chemical exposure could have impacted genes passed from an exposed father, said study author Katherine Greeson.

"It is still a relatively new idea that a man's exposures prior to conception can impact the health of his children," said Greeson, an environmental health science doctoral student in Charles Easley's lab at UGA's College of Public Health and Regenerative Bioscience Center.

"Most studies where a toxic effect is observed in children look only to the mothers and the same has been true of studies conducted on PBB153," she said.

Greeson and a team of researchers from UGA and Emory University used a unique combination of observational and laboratory approaches to demonstrate how PBB153 acted on sperm cells.

"Typically, scientific studies are either epidemiological in nature and inherently observational or focus on bench science, but in this study, we did both," said Greeson.

This approach allowed the researchers to mimic the known blood exposure levels of PBB153 in a lab environment.

"We were uniquely able to recreate this effect using our previously characterized human stem cell model for spermatogenesis," she said, "which allowed us to study the mechanism that causes this effect in humans."

The team looked at the expression of different genes in their human spermatogenesis model after dosing with PBB153 and found marked alterations in gene expression between dosed and undosed cells, specifically at genes important to development, such as embryonic organ, limb, muscle, and nervous system development.

"PBB153 causes changes to the DNA in sperm in a way that changes how the genes are turned on and off," said Greeson. "PBB153 seems to turn on these genes in sperm which should be turned off," said Greeson, which may explain some of the endocrine-related health issues observed in the children of exposed parents.

Though the study used this model to directly replicate exposure to PBB153, Greeson says this approach could be used to better understand the impact of other environmental exposures on reproduction, including large-scale accidental exposures to toxic chemicals or everyday exposures.

"Hopefully this work will lead to more studies combining epidemiology and bench science in the future, which will tell us more about why we're seeing an effect from an environmental exposure in human populations and encourage experimental studies to more closely mimic human exposures," she said.

The study, "Detrimental Effects of Flame Retardant, PBB153, Exposure on Sperm and Future Generations," published May 22.

Monitoring environmental exposures in dogs could be early warning system for human health

More information: Katherine Watkins Greeson et al, Detrimental effects of flame retardant, PBB153, exposure on sperm and future generations, Scientific Reports (2020). DOI: 10.1038/s41598-020-65593-x

Journal information: Scientific Reports

Provided by University of Georgia

Study finds another reason to wash hands: Flame retardants

by University of Toronto

Harmful flame retardants may be lurking on your hands and cell phone, according to a peer-reviewed study published today in Environmental Science & Technology Letters.

The researchers found that halogenated flame retardants added to plastic TV cases can move from the TV to indoor air and dust, to hands, and then to cell phones and other hand-held electronic devices. Once on your cell phone, that surface provides an ongoing source of exposure to these chemicals each time you touch your cell phone.

"It's well-known that viruses are transferred between surfaces and hands," said co-author Miriam Diamond, a Professor in the Department of Earth Sciences at the University of Toronto. "Our study shows that toxic chemicals like flame retardants do the same. That's another reason we should all wash our hands often and well."

Halogenated flame retardants, such as polybrominated diphenyl ethers, are known to pose a health risk to children. Previous studies have found that exposure to these chemicals can cause lower IQ in children and behavioral problems.

The authors were surprised to find higher levels of almost all halogenated flame retardants, all organophosphate flame retardants, and phthalate plasticizers on the surfaces of cell phones and other hand-held electronic devices like tablets, compared to non-hand-held devices like desktop computers. This included finding higher levels of long-banned polybrominated diphenyl ethers on new cell phones than on the surfaces of older desktop computers. The researchers suggest that these old chemicals got to the new phones by transfer from hands.

Why are TVs a source of flame retardants? The answer lies in the odd story of old "instant-on" cathode ray tube TVs manufactured in the 1970s. This technology, which involved warming the cathode ray tube so that the TV would immediately project an image when turned on, resulted in several hundred TV fires in the 1970s. The response was to recommend flammability standards that led to large amounts of flame retardants added to the outside casings of the TVs.

However, those same levels of flame retardants continued to be used —as much as a quarter of the weight of the plastic case— even after the industry moved to current TVs that pose a minimal fire risk. Thus, recently manufactured TVs contain high levels of unnecessary and harmful flame retardants. We are exposed because the flame retardants are not bonded to the cases, but escape over time to contaminate our indoor environments.

"If a flame retardant is used in the TVs, we then find it throughout the house, including on the hands of the resident," said co-author Lisa Melymuk, an Assistant Professor of Environmental Chemistry at Masaryk University.

The COVID-19 pandemic has taught us to wash our hands regularly and well to avoid getting ill. The results of this study suggest that frequent handwashing can also reduce our exposure to harmful flame retardants.

"However, to reduce health harm from flame retardants, the electronics industry should stop their unnecessary use," said Arlene Blum, Executive Director of the Green Science Policy Institute. "Fire safety can be achieved by innovative product design and materials instead of the use of toxic chemicals that can remain in our homes—and in us—for years to come."

New flame retardants, old problems

More information: Congqiao Yang et al, Are We Exposed to Halogenated Flame Retardants from both Primary and Secondary Sources?, Environmental Science & Technology Letters (2020). DOI: 10.1021/acs.estlett.0c00268

Journal information: Environmental Science & Technology Letters

Provided by University of Toronto

Renewable fuel from carbon dioxide with the aid of solar energy
by Linköping University

Researchers at Linköping University work with the growth reactor in which cubic silicon carbide is made. Credit: Thor Balkhed/Linköping University

Researchers at Linköping University, Sweden, are attempting to convert carbon dioxide, a greenhouse gas, to fuel using energy from sunlight. Recent results have shown that it is possible to use their technique to selectively produce methane, carbon monoxide or formic acid from carbon dioxide and water. The study has been published in ACS Nano.

Plants convert carbon dioxide and water to oxygen and high-energy sugars, which they use as "fuel" to grow. They obtain their energy from sunlight. Jianwu Sun and his colleagues at Linköping University are attempting to imitate this reaction, known as photosynthesis, used by plants to capture carbon dioxide from air and convert it to chemical fuels, such as methane, ethanol and methanol. The method is currently at a research stage, and the long-term objective of the scientists is to convert solar energy to fuel efficiently.

"By converting carbon dioxide to fuel with the aid of solar energy, this technique could contribute to the development of sources of renewable energy and reduce the impact on the climate of the combustion of fossil fuels," says Jianwu Sun, senior lecturer in the Department of Physics, Chemistry and Biology at Linköping University.

Graphene is one of the thinnest materials that exist, consisting of a single layer of carbon atoms. It is elastic, flexible, transparent to sunlight, and a good conductor of electricity. This combination of properties ensures that graphene has potential for use in applications such as electronics and biomedicine. But graphene alone is not suitable for the solar energy conversion application sought by the LiU researchers, and they have therefore combined the graphene with a semiconductor, cubic silicon carbide (3C-SiC). Scientists at Linköping University have previously developed a world-leading method to grow graphene on cubic silicon carbide, which consists of carbon and silicon. When the silicon carbide is heated, the silicon is vaporized, while the carbon atoms remain and re-construct in the form of a graphene layer. The researchers have previously shown that it is possible to place up to four layers of graphene on top of each other in a controlled manner.

Jianwu Sun, senior lecturer at Linköping University. Credit: Thor Balkhed/Linköping University

They have combined the graphene and cubic silicon carbide to develop a graphene-based photoelectrode that preserves the ability of cubic silicon carbide to capture the energy of sunlight and create charge carriers. The graphene functions as a conducting transparent layer while protecting the silicon carbide.

The performance of the graphene-based technique is controlled by several factors, an important one of which is the quality of the interface between the graphene and the semiconductor. The scientists have looked at the properties of this interface in detail. They show in the article that they can tailor the layers of graphene on the silicon carbide and control the properties of the graphene-based photoelectrode. The conversion of carbon dioxide is in this way made more efficient, while the stabilities of the components are at the same time improved.

The photoelectrode developed by the researchers can be combined with cathodes of various metals, such as copper, zinc or bismuth. Different chemical compounds, such as methane, carbon monoxide and formic acid, can be selectively formed from carbon dioxide and water by selecting suitable metal cathodes.

"Most importantly, we have demonstrated that we can use solar energy to control the conversion of carbon dioxide to methane, carbon monoxide or formic acid," says Jianwu Sun.

Methane is used as a fuel in vehicles adapted to use gaseous fuels. Carbon monoxide and formic acid can either be further processed such that they can function as fuels, or they can be used in industry."

Graphene takes a step toward renewable fuel
More information: Hao Li et al, Atomic-Scale Tuning of Graphene/Cubic SiC Schottky Junction for Stable Low-Bias Photoelectrochemical Solar-to-Fuel Conversion, ACS Nano (2020). DOI: 10.1021/acsnano.0c00986
Journal information: ACS Nano

Provided by Linköping University

Study on shorebirds suggests that when conserving species, not all land is equal

by Princeton University

Princeton researchers may have solved the long-standing puzzle of why migratory shorebirds around the world are plummeting several times faster than coastal ecosystems are being developed. They discovered that shorebirds overwhelmingly rely on the portion of tidal zones closest to dry land for food and rest as they migrate, which are the locations most often lost to development. The findings stress the need for integrating upper tidal flats into conservation plans focused on migratory shorebirds. Credit: Tong Mu, Department of Ecology and Evolutionary Biology

Princeton University researchers may have solved a long-standing mystery in conservation that could influence how natural lands are designated for the preservation of endangered species.

Around the world, the migratory shorebirds that are a conspicuous feature of coastal habitats are losing access to the tidal flats—the areas between dry land and the sea—they rely on for food as they travel and prepare to breed. But a major puzzle has been that species' populations are plummeting several times faster than the rate at which coastal ecosystems are lost to development.

Nowhere is the loss of tidal flats and shorebird species more acute than along the East Asia-Australasian Flyway (EAAF). An estimated 5 million migratory birds from 55 species use the flyway to travel from southern Australia to northern Siberia along the rapidly developing coast of China—where tidal flats can be more than 6 miles wide—at which birds stop to rest and refuel.

Since the 1980s, the loss of tidal flats around the Yellow Sea has averaged 1.2% per year. Yet, the annual loss of the most endangered bird species has averaged between 5.1 and 7.5%, with populations of species such as the critically endangered spoon-billed sandpipers (Calidris pygmaea) climbing as high as 26% each year.

In exploring this disparity, Princeton researchers Tong Mu and David Wilcove found a possible answer—the birds don't use all parts of the tidal flat equally. They discovered that migratory shorebirds overwhelmingly rely on the upper tidal flats closest to dry land, which are the exact locations most often lost to development.

They report in the journal Proceedings of the Royal Society B that China's upper tidal flats provided more than 70% of the cumulative foraging time for the species they studied at two Yellow Sea sites along the EAAF. The middle and lower flats that birds are increasingly pushed toward by human activity were less frequently foraged upon due to the tide cycle, which may be impacting species health and breeding success.

The findings stress the need for integrating upper tidal flats into conservation plans focused on migratory shorebirds, the authors reported.

A key difference of the Princeton research was that it included observations of the high-tide period when the middle and lower tidal flats are underwater. The researchers focused on the East Asia-Australasian Flyway, which spans from Australia to Siberia along the rapidly developing coast of China where birds stop to rest and refuel. The researchers studied birds at two well-known stopover sites in the Yellow Sea region, Nanpu (b) near Beijing and Rudong (c) outside of Shanghai. The dark squares indicate the study plots along the upper, middle and lower tidal flats (dotted area). The white areas represent the sea beyond the low-tide line. Credit: Tong Mu, Department of Ecology and Evolutionary Biology

"This is a new insight into Asian shorebirds, but I suspect that the upper intertidal is disproportionately important to shorebirds in other places, too, such as the East and West coasts of North America," said Wilcove, who is a professor of ecology and evolutionary biology and public affairs and the Princeton Environmental Institute (PEI).
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"People start at the upper zone and work their way outward, so the best spots for the birds are the first to go," he said. "It would probably be best to extend current developments farther into the intertidal zone rather than keep building parallel to the coast, which consumes more of the upper intertidal.

"Think of it as advocating for a rectangle with the long side pointing into the sea versus a rectangle with the long side hugging the shore," Wilcove said.

The study results also suggest that protecting species and their habitats may mean more than designating land for wildlife—it may require identifying the right land to set aside by gaining a detailed understanding of exactly how animals interact with the landscape.

"Recognizing the importance of a kind of habitat to specific species or groups of species takes time, effort and thought," said Mu, who is the paper's first author and a Ph.D. candidate in ecology and evolutionary biology.

"Sometimes we just don't know what to look for, or looking requires challenging some prevalent and maybe false perceptions," he said. "But the situation is getting better and better. People are paying more attention to environmental issues, and the advances in technology are helping us gain more and newer insight into these questions."

Mu conducted fieldwork between September 2016 and May 2017 at two well-known stopover sites—one outside of Beijing, the other near Shanghai—for migratory shorebirds in the Yellow Sea region. He focused on 17 species of birds, noting where along the tidal flat the animals preferred to feed.

The findings suggest that protecting species requires gaining a detailed understanding of exactly how animals interact with the landscape so that preserved habitats best serve endangered species' needs. Since the 1980s, the loss of tidal flats around the Yellow Sea has averaged 1.2% per year. Yet, the annual loss of the most endangered bird species has averaged between 5.1 and 7.5%, with populations of species such as the critically endangered spoon-billed sandpiper (Calidris pygmaea) climbing as high as 26% each year. Credit: Tong Mu, Department of Ecology and Evolutionary Biology

A key difference to his approach, Mu said, is that most previous research focused on the low-tide period when all the tidal flats are exposed and the full range of intertidal species can be observed.

"It makes sense from an ecological point of view. During the high tides when only a portion of the tidal flats is accessible, the relationship usually still holds for the exposed area," Mu said. "So, there's little incentive to look at the periods other than low tide when researchers can get a more complete picture."

What Mu thinks was missed, however, was that the upper tidal flats provide the most amount of foraging time for birds that have places to be. Even if the lower half of a 6-mile wide mudflat is set aside for migratory birds, they're not getting the energy they need for the trip ahead during the high tide, he said.

"The value of the tidal flats comes from not only their size, but also how much foraging time they can provide," Mu said. "The upper tidal area is exposed for a longer period during tidal cycles, compared to the middle and lower areas, which I think permits shorebirds to forage for a longer time and thus get more energy."

The preservation of shorebirds should be driven by how integral the animals are to the health of intertidal zones, Mu and Wilcove said. In turn, tidal flats are not only vital to other marine life, but also provide people with seafood such as clams and crabs and protection from storms and storm surges that cause coastal flooding.

"Shorebirds facilitate the energy and nutrient exchanges between land and sea," Mu said. "Because a lot of them are long-distance migrants, they also facilitate the energy and nutrient exchanges across different ecosystems and continents, something that is usually overlooked and underappreciated."

Wilcove and Mu cited recent research showing that more than 15%, or more than 12,000 square miles, of the world's natural tidal flats were lost between 1984-2016.

"Some of the greatest travelers on Earth are the shorebirds that migrate from Siberia to Southeast Asia and Australia," Wilcove said. "Now, they're declining in response to the loss of the tidal areas, and the full range of benefits those tidal flats provide are in some way being diminished."
Australia migratory bird levels plunge from Asia development
More information: Tong Mu et al, Upper tidal flats are disproportionately important for the conservation of migratory shorebirds, Proceedings of the Royal Society B: Biological Sciences (2020). DOI: 10.1098/rspb.2020.0278
Journal information: Proceedings of the Royal Society B

Provided by Princeton University

Volcanic activity and changes in Earth's mantle were key to rise of atmospheric oxygen

by Hannah Hickey, University of Washington

Oxygen first accumulated in the Earth's atmosphere about 2.4 billion years ago, during the Great Oxidation Event. A long-standing puzzle has been that geologic clues suggest early bacteria were photosynthesizing and pumping out oxygen hundreds of millions of years before then. Where was it all going?

Something was holding back oxygen's rise. A new interpretation of rocks billions of years old finds volcanic gases are the likely culprits. The study led by the University of Washington was published in June in the open-access journal Nature Communications.

"This study revives a classic hypothesis for the evolution of atmospheric oxygen," said lead author Shintaro Kadoya, a UW postdoctoral researcher in Earth and space sciences. "The data demonstrates that an evolution of the mantle of the Earth could control an evolution of the atmosphere of the Earth, and possibly an evolution of life."

Multicellular life needs a concentrated supply of oxygen, so the accumulation of oxygen is key to the evolution of oxygen-breathing life on Earth.

"If changes in the mantle controlled atmospheric oxygen, as this study suggests, the mantle might ultimately set a tempo of the evolution of life," Kadoya said.

The new work builds on a 2019 paper that found the early Earth's mantle was far less oxidized, or contained more substances that can react with oxygen, than the modern mantle. That study of ancient volcanic rocks, up to 3.55 billion years old, were collected from sites that included South Africa and Canada.

Robert Nicklas at Scripps Institution of Oceanography, Igor Puchtel at the University of Maryland, and Ariel Anbar at Arizona State University are among the authors of the 2019 study. They are also co-authors of the new paper, looking at how changes in the mantle influenced the volcanic gases that escaped to the surface.

The Archean Eon, when only microbial life was widespread on Earth, was more volcanically active than today. Volcanic eruptions are fed by magma—a mixture of molten and semi-molten rock—as well as gases that escape even when the volcano is not erupting.

Some of those gases react with oxygen, or oxidize, to form other compounds. This happens because oxygen tends to be hungry for electrons, so any atom with one or two loosely held electrons reacts with it. For instance, hydrogen released by a volcano combines with any free oxygen, removing that oxygen from the atmosphere.

The chemical makeup of Earth's mantle, or softer layer of rock below the Earth's crust, ultimately controls the types of molten rock and gases coming from volcanoes. A less-oxidized early mantle would produce more of the gases like hydrogen that combine with free oxygen. The 2019 paper shows that the mantle became gradually more oxidized from 3.5 billion years ago to today.

The new study combines that data with evidence from ancient sedimentary rocks to show a tipping point sometime after 2.5 billion years ago, when oxygen produced by microbes overcame its loss to volcanic gases and began to accumulate in the atmosphere.

"Basically, the supply of oxidizable volcanic gases was capable of gobbling up photosynthetic oxygen for hundreds of millions of years after photosynthesis evolved," said co-author David Catling, a UW professor of Earth and space sciences. "But as the mantle itself became more oxidized, fewer oxidizable volcanic gases were released. Then oxygen flooded the air when there was no longer enough volcanic gas to mop it all up."

This has implications for understanding the emergence of complex life on Earth and the possibility of life on other planets.

"The study indicates that we cannot exclude the mantle of a planet when considering the evolution of the surface and life of the planet," Kadoya s

Buried oxygen rose to the occasion as Earth's early atmosphere formed

More information: Shintaro Kadoya et al, Mantle data imply a decline of oxidizable volcanic gases could have triggered the Great Oxidation, Nature Communications (2020). DOI: 10.1038/s41467-020-16493-1

Journal information: Nature Communications

Provided by University of Washington

Sharing of tacit knowledge is most important aspect of mentorship, study finds

by Northwestern University

When it comes to education and mentorship, Northwestern University researchers believe that Albert Einstein had the right idea. The most important aspect of teaching, Einstein thought, isn't relaying facts but imparting tacit knowledge that students will build on for the rest of their lives.

In one of the largest ever multidisciplinary investigations into mentorship and mentee performance, the Kellogg School of Management researchers found that the most impactful mentors are those who teach students to think independently and communicate their unique viewpoints effectively.

"Communicating codified knowledge is relatively straightforward," said corresponding author Brian Uzzi. "It's written down in books and presentations. But it's the unwritten knowledge we intuitively convey through our interactions and demonstrations with students that makes a real difference for mentees."

The researchers note that remote learning, which is becoming more common during the COVID-19 pandemic, may not be as effective a means of transferring such tacit knowledge, which could have long-term effects.

"Face-to-face interaction is essential. When we teach by doing, we are conveying tacit knowledge we don't even realize we have," said Uzzi, the Richard L. Thomas Professor of Leadership at Northwestern's Kellogg School of Management and co-director of the Northwestern Institute on Complex Systems. "If we limit the face-to-face channel by which tacit knowledge is communicated, we potentially slow down the pace of learning and scientific breakthroughs, and that will affect us all."

When mentors excel in transferring tacit knowledge, their protégés achieve two to four times greater success than similarly talented students of mentors who convey regimented knowledge but not tacit know-how, the researchers found. Protégé success was determined by whether they won a scientific prize of their own during their career, were elected to the National Academy of Sciences or were in the top 25% of citations for their field.

The most successful protégés also were more likely to pioneer their own research topics, rather than follow in their mentors' research path. This finding contradicts the popular belief that the most successful protégés will be those who carry on their mentors' already successful work.

The study, "Mentorship and protégé success in science," publishes the week of June 8 in PNAS. The study is among the first to look at objective protégé performance over the course of a career, drawing from genealogical datasets that track the relationships between mentors and students.

Previous research into the topic of mentorship has been done largely through self-reporting, often many years after the students graduate. That makes it subject to memory errors and personal biases, researchers say.

The researchers studied genealogical data on 40,000 scientists who published 1.2 million papers in biomedicine, chemistry, math or physics between 1960 and 2017. They also used the ProQuest Dissertations and Theses databank, an official record of advisor/student relationships taken from Ph.D. theses, and supplemented it with additional crowdsourced data from AcademicTree.org and the Mathematics Genealogy Project to ensure they correctly matched mentor/mentee relationships.

To account for the fact that more successful mentors naturally attract more talented students, the researchers grouped mentors with similar records and reputation based on factors including institutional resources, productivity, number of students, citations and other measures of a mentor's skills, and they compared the performance of students within the same mentor peer group. However, one mentor in each peer group had a hidden talent for identifying key problems and producing compelling solutions that the other mentors did not have. These mentors were future scientific prizewinners.

To assess protégé success, the researchers considered only those students who studied under a mentor before that mentor won their scientific prize to control for selection bias and the halo effect a prizewinning mentor casts over their students.

After controlling for differences in mentorship skills and mentee talent, the researchers found that the most successful protégés studied under mentors who demonstrated a unique skill in ideating and publishing celebrated research and who displayed independent thought by breaking away from their mentors' lines of resea

Childhood mentors have positive impact on career success

More information: Yifang Ma el al., "Mentorship and protégé success in science," PNAS (2020). www.pnas.org/cgi/doi/10.1073/pnas.1915516117

Journal information: Proceedings of the National Academy of Sciences

Provided by Northwestern University

What do electric vehicle drivers think of the charging network they use?

by Georgia Institute of Technology

With electric vehicles making their way into the mainstream, building out the nationwide network of charging stations to keep them going will be increasingly important.

A new study from the Georgia Institute of Technology School of Public Policy harnesses machine learning techniques to provide the best insight yet into the attitudes of electric vehicle (EV) drivers about the existing charger network. The findings could help policymakers focus their efforts.

In the paper, published in the June 2020 issue the journal Nature Sustainability, a team led by Assistant Professor Omar Isaac Asensio describes training a machine learning algorithm to analyze unstructured consumer data from 12,270 electric vehicle charging stations across the U.S.

The study demonstrates how machine learning tools can be used to quickly analyze streaming data for policy evaluation in near-real time. Streaming data refers to data that comes in a continuous feed, such as user reviews from an app. The study also revealed surprising findings about how EV drivers feel about charging stations.

For instance, the conventional wisdom that drivers prefer private stations to public ones appears to be wrong. The study also finds potential problems with charging stations in larger cities, presaging challenges yet to come in creating a robust charging system that meets all drivers' needs.

"Based on evidence from consumer data, we argue that it is not enough to just invest money into increasing the quantity of stations, it is also important to invest in the quality of the charging experience," Asensio wrote.

Perceived Lack of Charging Stations a Barrier to Adoption

Electric vehicles are considered a crucial part of the solution to climate change: transportation is now the leading contributor of climate-warming emissions. But one major barrier to broader adoption of electric vehicles is the perception of a lack of charging stations, and the attending "range anxiety" that makes many drivers nervous about buying an EV.

While that infrastructure has grown considerably in recent years, the work hasn't taken into account what consumers actually want, Asensio said.

"In the early years of EV infrastructure development, most policies were geared to using incentives to increase the quantity of charging stations," Asensio said. "We haven't had enough focus on building out reliable infrastructure that can give confidence to users."

This study helps rectify that shortcoming by offering evidence-based, national analysis of actual consumer sentiment, as opposed to indirect travel surveys or simulated data used in many analyses.

Asensio directed the study with a team of five students in public policy, engineering, and computing. Two were from Georgia Tech: Catharina Hollauer, a recent graduate of the H. Milton School of Industrial and Systems Engineering, and Sooji Ha, a dual Ph.D. student in the School of Civil and Environmental Engineering and the School of Computational Science and Engineering.

The other three were participants in the 2018 Georgia Tech Civic Data Science Fellows program, which draws talented students from around the country to the Georgia Tech campus for a summer of research and learning. They are Kevin Alvarez of North Carolina State University, Arielle Dror of Smith College, and Emerson Wenzel of Tufts University.

EV Charging Sore Spots Revealed

Asensio's team used deep learning text classification algorithms to analyze data from a popular EV users smartphone app. It would have taken most of a year using conventional methods. But the team's approach cut the task down to minutes while classifying sentiment with accuracy similar to that of human experts.

The study found that workplace and mixed-use residential stations get low ratings, with frequent complaints about lack of accessibility and signage. Fee-based charging stations tend to get more poor reviews than free charging stations. But it is stations in dense urban centers that really draw complaints, according to the study.

When researchers controlled for location and other characteristics, stations in dense urban areas showed a 12—15% increase in negative sentiment compared to nonurban locations.

This could indicate a broad range of service quality issues in the largest EV markets, including things like malfunctioning equipment and an insufficient number of chargers, Asensio said.

The highest rated stations are often located at hotels, restaurants, and convenience stores, a finding that may support incentive-based management practices in which chargers are installed to draw customers. Stations at public parks and recreation facilities, RV parks, and visitor centers also do well, according to the study.

But, contrary to theories predicting that private stations should provide more efficient services, the study found no statistically significant difference in user preferences when it comes to public versus private chargers.

That finding could be an inducement to invest in public charging infrastructure to meet future growth, Asensio said. Such a network was cited in a study by the National Research Council as key to helping overcome barriers to EV adoption.

Improving Policy Evaluation Beyond EV's

Overall, Asensio said the study points to the need to prioritize consumer data when considering how to build out infrastructure, especially when it comes to requirements for charging stations in new buildings.

But EV policy is not the only way the study's deep learning techniques can be used to analyze this kind of material. They could be adapted to a broad range of energy and transportation issues, allowing researchers to deliver rapid analysis with just minutes of computation, compared to time lags measured sometimes in months or years using more traditional methods.

"The follow-on potential for energy policy is to move toward automated forms of infrastructure management powered by machine learning, particularly for critical linkages between energy and transportation systems and smart cities," Asensio said.

Tesla puts charging stations in more locations

More information: Omar Isaac Asensio et al, Real-time data from mobile platforms to evaluate sustainable transportation infrastructure, Nature Sustainability (2020). DOI: 10.1038/s41893-020-0533-

Journal information: Nature Sustainability

Provided by Georgia Institute of Technology

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